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second brain
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The Second Brain: Your Gut Has 500 Million Neurons — and the Vagus Is How It Reports to HQ
Buried in the wall of your intestines is a neural network so large and so independent that scientists genuinely call it a second brain. It has roughly 500 million neurons, runs digestion on its own, and makes most of your body's serotonin. The vagus is the cable connecting it to the brain in your skull — and understanding that link explains why the gut has such power over mood.
By VagusSkool Team
Jul 22, 2026